Our major objective is to isolate and characterize abnormal membrane components that are specific to or associated with human leukemia cells or malignant lymphoma cells, as well as to isolate normal membrane components, especially normal alloantigenic components of human lymphocytes that are linked to immunologic functions. Particular effort is directed to identification and isolation of the human homologues of mouse TL (thymus-leukemia) antigens, mouse Ia (I-region-associated) antigens and mouse Ly antigens and to further characterization of HLA (A,B,C) antigens. Human lymphoid cell lines, T-cell-type, B-cell-type and null-cell-type, are being used for this purpose, since they retain a variety of biological functions and represent a uniform cell population whose supply can be relatively unlimited in amount. We also plan to produce T-cell hybrid clones which possess known immunological functions and to use them for the present purpose. We also investigate similar cell surface antigens in cells of malignant cell lines derived from sarcoma and/or carcinoma which are available in this laboratory. The very sensitive quantitative radioimmunoassay method involving the use of radiolabeled reference antigens which has been extensively employed by us in earlier studies facilitates identification and isolation of the membrane components.